This invention relates to an adjustable shock absorber and system that allow remote adjustment of the force-velocity response of the shock absorber.
There is considerable interest in the automotive industry in a low cost reliable adjustable shock absorber that allows adjustment of its force-velocity response in accordance with either driver or automatic input signals. Knecht U.S. Pat. No. 4,650,042, Ashiba U.S. Pat. No. 4,519,186 and Emura U.S. Pat. No. 4,620,619 all disclose shock absorbers which utilize electrically powered actuators in the shock absorber to modify damping characteristics. Similarly Ellis U.S. Pat. No. 4,122,923 and Schupner U.S. Pat. No. 4,164,274 disclose adjustable shock absorbers having manually adjusted mechanical linkages to set the damping characteristics.
The above-identified prior art approaches use either electric motor or manually adjusted mechanical linkages to position valving elements at predetermined locations in the shock absorber. In many cases, such adjustable shock absorbers suffer from the need for a relatively expensive hollow piston rod. Furthermore, each unit must be made to close tolerances so that all the units on a given vehicle change in the same manner as the electric motors or mechanical linkages are adjusted.
Williams U.S. Pat. No. 4,753,328 discloses a shock absorber system in which pneumatic circuits are used to modify the effective length of the shock absorbers, not to change damping characteristics. In some ways. Williams is similar to Kuroki U.S. Pat. No. 4,600,215 and Kanai U.S. Pat. No. 4,566,718, both of which disclose conventional air spring systems in which pneumatic circuits are used to vary the characteristics of a plurality of air springs simultaneously.
The present invention is directed to an improved adjustable shock absorber and system which solve many of the problems of the prior art systems described above by eliminating the need for electric motor actuators or manually adjusted mechanical linkages to adjust the damping characteristics of the shock absorber.